U.S. patent application number 12/313660 was filed with the patent office on 2009-05-28 for surgical obturator.
This patent application is currently assigned to Aesculap AG. Invention is credited to Johann Maliglowka, Rupert Mayenberger, Tom Schweitzer.
Application Number | 20090138034 12/313660 |
Document ID | / |
Family ID | 38326490 |
Filed Date | 2009-05-28 |
United States Patent
Application |
20090138034 |
Kind Code |
A1 |
Maliglowka; Johann ; et
al. |
May 28, 2009 |
Surgical obturator
Abstract
In a surgical obturator for piercing a body wall, comprising a
tubular housing that at one end forms an introduction tip with a
continuously decreasing diameter, and comprising a blade projecting
from the introduction tip for making an incision in the body wall,
in order to reduce the risk of injury during piercing of the body
wall it is proposed that the introduction tip comprises a central
protective cap, which is displaceable in longitudinal direction
relative to the introduction tip between an advanced inoperative
position and a retracted working position, that the blade in the
housing is displaceable in longitudinal direction between an
advanced cutting position and a retracted protected position, that
disposed in the housing is a retraction device that displaces the
blade from the cutting position into the protected position, and
that the retraction device may be activated by a displacement of
the protective cap from the working position into the inoperative
position.
Inventors: |
Maliglowka; Johann;
(Kolbingen, DE) ; Mayenberger; Rupert;
(Rielasingen, DE) ; Schweitzer; Tom; (Tuttlingen,
DE) |
Correspondence
Address: |
Lipsitz & McAllister, LLC
755 MAIN STREET
MONROE
CT
06468
US
|
Assignee: |
Aesculap AG
Tuttlingen
DE
|
Family ID: |
38326490 |
Appl. No.: |
12/313660 |
Filed: |
November 21, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2007/003881 |
May 3, 2007 |
|
|
|
12313660 |
|
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|
Current U.S.
Class: |
606/185 |
Current CPC
Class: |
A61B 17/3496 20130101;
A61B 17/3474 20130101 |
Class at
Publication: |
606/185 |
International
Class: |
A61B 17/34 20060101
A61B017/34 |
Foreign Application Data
Date |
Code |
Application Number |
May 27, 2006 |
DE |
10 2006 024 757 |
Claims
1-18. (canceled)
19. Surgical obturator for piercing a body wall, comprising a
tubular housing that at one end forms an introduction tip with a
continuously decreasing diameter, comprising a blade projecting
from the introduction tip for making an incision in the body wall,
and comprising a protective element, which is displaceable in
longitudinal direction relative to the housing between an advanced
inoperative position and a retracted working position, wherein the
blade in the housing is displaceable in longitudinal direction
between an advanced cutting position and a retracted protected
position, wherein disposed in the housing is a retraction device
that displaces the blade from the cutting position into the
protected position, and wherein the retraction device can be
activated by a displacement of the protective element from the
working position into the inoperative position, wherein the
introduction tip is subdivided into two portions, namely a proximal
portion, which is part of the housing, and a central protective cap
forming the protective element, wherein the outer surface of the
protective cap in the retracted working position merges
continuously into the outer surface of the proximal portion,
whereas in the advanced inoperative position a step is formed
between the protective cap and the proximal portion of the
introduction tip, and wherein the blade in the cutting position
projects in the region of the retracted protective cap and in an
adjoining region of the proximal portion from the contour of the
protective cap and of the proximal portion.
20. Surgical obturator according to claim 19, wherein the blade in
the protected position is retracted to such an extent that it also
no longer projects from the protective cap in the working position
thereof.
21. Surgical obturator according to claim 19, wherein the
protective cap is acted upon by a spring that displaces the
protective cap from the working position into the inoperative
position.
22. Surgical obturator according to claim 19, wherein the blade in
the cutting position does not project from the contour of the
proximal portion of the introduction tip in the proximal end region
thereof.
23. Surgical obturator according to claim 19, wherein the
introduction tip is of a truncated-cone-shaped configuration and
has a rounded tip.
24. Surgical obturator according to claim 19, wherein the blade is
held on a blade carrier, which is mounted in a longitudinally
displaceable manner in the housing and which is displaceable by
means of a spring into a retracted position, in which the blade is
in the protected position.
25. Surgical obturator according to claim 24, wherein the blade
carrier carries a gripping element for displacing the blade carrier
into the advanced position.
26. Surgical obturator according to claim 24, wherein the
retraction device comprises a catch, which during advancing locks
the blade carrier in the advanced position.
27. Surgical obturator according to claim 26, wherein the
protective cap during advancing from the working position into the
inoperative position releases the catch and hence triggers the
return movement of the blade carrier into the retracted
position.
28. Surgical obturator according to claim 27, wherein the
protective cap in the working position displaces a locking element
into a position fixing the catch in a detent position and during
advancing into the inoperative position removes the locking element
from this position.
29. Surgical obturator according to claim 28, wherein the catch is
held by means of a blocking member in a position fixing the catch
in a detent position and wherein the protective cap in the working
position removes the blocking member from the catch and at the same
time displaces the locking element into the position fixing the
catch, so that the catch remains continuously in its detent
position.
30. Surgical obturator according to claim 29, wherein the blocking
member is mounted on the blade carrier.
31. Surgical obturator according to claim 30, wherein the blocking
member is mounted displaceably on the blade carrier.
32. Surgical obturator according to claim 31, wherein the blocking
member is a sliding ring that surrounds the blade carrier and is
freely displaceable between two end positions.
33. Surgical obturator according to claim 26, wherein the catch is
a spring-loaded pivotal lever.
34. Surgical obturator according to claim 26, wherein the catch and
the blade carrier have sliding faces, which, when the catch is not
fixed in the detent position and the blade carrier is being pushed
back, slide along one another and in so doing move the catch into a
release position.
35. Surgical obturator according to claim 19, wherein the blade has
a helical-line-shaped cutting edge.
36. Surgical obturator according to claim 22, wherein the blade has
a helical-line-shaped cutting edge.
37. Surgical obturator according to claim 23, wherein the blade has
a helical-line-shaped cutting edge.
Description
[0001] The invention relates to a surgical obturator for piercing a
body wall, comprising a tubular housing that at one end forms an
introduction tip with a continuously decreasing diameter, and
comprising a blade projecting from the introduction tip for making
an incision in the body wall.
[0002] Such obturators are used to form openings in a body wall for
a cannula or a tube, which tube may be for example a trocar tube,
through which instruments are introduced into the body.
[0003] When the obturator is being advanced, there is a risk that
the obturator, once it has passed right through the body wall, may
be advanced further in an uncontrolled manner and the blade
disposed on the front end of the obturator may cause injury to
internal organs.
[0004] It is therefore known to provide such obturators with a
protective shield, which after passage through the body wall is
pushed forward and covers the blade (WO89/03661). Advancing the
protective shield can likewise lead to injuries, as it often shoots
forward abruptly under the action of a spring, and it is moreover
usually necessary for the obturator to have fully penetrated the
body wall before activation of the protective shield may occur.
[0005] The object of the invention is to design a surgical
obturator of the above general type in such a way that the risk of
an injury to internal organs during piercing of a body wall is
reduced.
[0006] In a surgical obturator of the type described in the
introduction, this object is achieved according to the invention in
that the introduction tip comprises a central protective cap, which
is displaceable in longitudinal direction relative to the
introduction tip between an advanced inoperative position and a
retracted working position, that the blade in the housing is
displaceable in longitudinal direction between an advanced cutting
position and a retracted protected position, that disposed in the
housing is a retraction device that displaces the blade from the
cutting position into the protected position, and that the
retraction device can be activated by a displacement of the
protective cap from the working position into the inoperative
position.
[0007] With such a development, the protection is effected by an
active retraction of the blade into the housing. This retraction
device is activated by the movement of a central protective cap,
which in a working position is retracted and in an inoperative
position is advanced. Such a protective cap is displaced into the
working position by the positioning of the obturator against the
body wall and moves during piercing of the body wall into the
advanced inoperative position because the protective cap then no
longer rests against the body wall and is therefore pushed back
into the working position. This advancing movement of the
protective cap is utilized in order immediately to retract the
blade to such an extent that it no longer projects from the
protective cap and the introduction tip, with the result that there
is also no longer any risk of injury.
[0008] In this case, it is advantageous if the protective cap is
acted upon by a spring that displaces the protective cap from the
working position into the inoperative position. This occurs
immediately after the piercing of the body wall, in which case the
advancing movement of the protective cap may be very slight so that
there is no danger of the protective cap causing an injury as a
result of the advancing movement.
[0009] In particular it is provided that the blade in the protected
position is retracted to such an extent that it also no longer
projects from the protective cap in the working position thereof.
Thus, even if the protective cap should come to lie against an
internal organ and therefore be displaced once more into the
working position, there is no risk of the blade coming into contact
with internal organs. With the use of a protective shield that
overlaps the blade, there is the risk that the protective shield
may be accidentally pushed back and may then release the blade. In
order to prevent that, special complicated locking devices have to
be provided, which hold the protective shield in the advanced
position. With the described design, this problem is eliminated
because the blade remains in a retracted, protected position once
the retraction device has been activated by the advancing of the
protective cap.
[0010] In the cutting position the blade projects in the region of
the retracted protective cap and in an adjoining region of the
introduction tip from the contour of the protective cap and of the
introduction tip.
[0011] In this case, it is advantageous if the blade in the cutting
position does not project from the contour of the introduction tip
in the proximal end region thereof. As a result of such a
development, during piercing of the body wall an incision is made
only in a central region of the introduction tip, not however in
the region of the proximal edge. When the obturator is advanced
further, the introduction tip, the diameter of which increases in
proximal direction, enters the body wall through the opening
produced by the incision and expands this opening without
additional cutting in the end region. The result is therefore a
relatively non-invasive production of an opening and moreover a
good seal between the body wall and the obturator, so that it is
optionally possible also to achieve a substantially gas-tight seal.
This is important in the event of insufflation of the body cavity
and when using sealed obturators.
[0012] In particular, the introduction tip may be of a
truncated-cone-shaped configuration and have a rounded tip. In this
case, the central part of the introduction tip is formed as a rule
by the protective cap.
[0013] The use of a central protective cap to activate the
retraction device moreover has the advantage that a retraction of
the blade may already be initiated before the introduction tip has
passed completely through the body wall. It is actually sufficient
for the central protective cap, the outside diameter of which is
smaller than the outside diameter of the introduction tip, to have
passed through the body wall for a retraction of the blade to
occur, despite the introduction tip not yet having been pushed
completely through the body wall. By selecting the dimensions of
the protective cap relative to the remaining introduction tip it is
possible to define the instant, at which during piercing a
retraction of the blade occurs. The smaller the diameter of the
protective cap in relation to the diameter of the introduction tip,
the earlier the activation of the retraction device occurs.
[0014] In a preferred embodiment, the blade is held on a blade
carrier, which is mounted in a longitudinally displaceable manner
in the housing and which is displaceable by means of a spring into
a retracted position, in which the blade is situated in the
protected position.
[0015] The blade carrier may carry a gripping element for
displacing the blade carrier into the advanced position.
[0016] It is advantageous if the retraction device comprises a
catch, which during advancing locks the blade carrier in the
advanced position.
[0017] Given such a development, it may be provided that the
protective cap during advancing from the working position into the
inoperative position releases the catch and hence triggers the
return movement of the blade carrier into the retracted
position.
[0018] In a particularly preferred embodiment, the protective cap
in the working position displaces a locking element into a position
fixing the catch in a detent position and during advancing into the
inoperative position removes the locking element from this
position. As a result of the removal of the blocking element the
catch is released and allows the blade carrier to move back into
the protected position of the blade.
[0019] Of particular advantage is a development, in which the catch
is held by a blocking member in a position fixing the catch in a
detent position and in which the protective cap in the working
position removes the blocking member from the catch and at the same
time displaces the locking element into the position fixing the
catch, in which case the catch remains constantly in its detent
position.
[0020] Such a development allows a locking of the catch in the
detent position even when the protective cap is not yet in working
position, i.e. is still advanced in the inoperative position. As
soon as the protective cap during piercing of the body wall is
positioned against the outside of the body wall, it is therefore
displaced into the working position and in this case replaces the
blocking member with the locking element, i.e. the protective cap
itself performs the function of locking the catch. Thus, the catch
at the start of the operation is fixed in the detent position by
means of the blocking member so long as the protective cap is still
situated in the advanced inoperative position and the obturator has
not yet been positioned against the body wall. At the start of the
piercing operation, the protective cap as a result of being
positioned against the body wall is retracted and effects the
fixing of the catch in the detent position. This fixing lasts until
the protective cap, after piercing, is advanced into the
inoperative position and hence releases the catch. This leads to
retracting of the blade.
[0021] The blocking member may be mounted on the blade carrier,
wherein the mounting is in particular a displaceable mounting.
[0022] For example, the blocking member may be a sliding ring that
surrounds the blade carrier and is freely displaceable between two
end positions.
[0023] It is advantageous if the catch is a spring-loaded pivoted
lever.
[0024] The catch and the blade carrier may have sliding faces,
which, when the catch is not fixed in the detent position and the
blade carrier is being pushed back, slide along one another and in
so doing move the catch in a release position. The catch is
therefore released in that the blade carrier is loaded with a force
in the direction of the protected position of the blade, for
example by means of a spring.
[0025] The shape of the blade may differ widely, being for example
V-shaped, a blade having a helical-line-shaped cutting edge being
particularly advantageous. Such a helical-line-shaped cutting edge
facilitates the delicate insertion of the obturator into a body
wall and also results in the blade during retraction being moved,
by virtue of the guidance of the blade in a guide slot of the
protective cap, helically and hence in accordance with the piercing
motion that the surgeon carries out likewise in a
helical-line-shaped manner.
[0026] The following description of preferred embodiments of the
invention is used in connection with the drawings to provide a
detailed explanation. The drawings show:
[0027] FIG. 1: a perspective view of an obturator in the region of
the introduction tip;
[0028] FIG. 2: a plan view of the obturator of FIG. 1;
[0029] FIG. 3: a detail view of a blade with a helical-line-shaped
cutting edge;
[0030] FIGS. 4 to 7: various embodiments of preferred contours of
cutting edges;
[0031] FIG. 8: a partial longitudinal section through a housing of
an obturator with a retraction device for the blade in a state
corresponding to the retracted protected position of the blade;
[0032] FIG. 9: a view similar to FIG. 8 during the advancing of the
blade from the protected position into the cutting position;
[0033] FIG. 10: a view similar to FIG. 9 with the blade fully
advanced;
[0034] FIG. 11: a view similar to FIG. 1 with an obturator prior to
positioning against a body wall and prior to displacement of the
protective cap into the working position;
[0035] FIG. 12: a view similar to FIG. 10 with the blade carrier
advanced and locked in the cutting position;
[0036] FIG. 13: a view similar to FIG. 11 with the obturator during
piercing of a body wall with the protective cap in working
position;
[0037] FIG. 14: a view similar to FIG. 12 with a pushed-back blade
carrier;
[0038] FIG. 15: a diagrammatic side view of the obturator of FIG. 1
after piercing of the body wall and after retraction of the blade
and
[0039] FIG. 16: a view similar to FIG. 14 during the return
movement of the blade carrier into the protected position of the
blade.
[0040] The obturator 1 represented in the drawings comprises a
tubular housing 2, of which in FIGS. 1, 11, 13 and 15 in each case
only the front part is shown. The housing 2 terminates in this
front part with a truncated-cone-shaped introduction tip 3, the tip
4 of which is rounded. The introduction tip 3 is subdivided into
two portions, namely a proximal portion 5, which is part of the
housing 2, and a central protective cap 6, which is displaceable
relative to the housing and hence relative to the proximal portion
5 in axial direction between two end positions, namely a retracted
(proximal) working position and an advanced (distal) inoperative
position. In the retracted working position the outer surface of
the protective cap 6 merges continuously into the outer surface of
the proximal portion 5 (FIG. 13), in the advanced inoperative
position a step 7 is formed between the protective cap 6 and the
proximal portion 5 of the introduction tip 3 (FIG. 1).
[0041] Running through its tip 5 the protective cap 6 has a slot 8,
which extends as far as into the proximal portion 5 of the
introduction tip 3 but terminates in the region of this proximal
region 5, i.e. does not extend as far as the proximal end of the
proximal portion 5.
[0042] Projecting through this slot 8 is a blade 9, the cutting
edge of which in the illustrated embodiment is of a
helical-line-shaped configuration, this shape corresponding also to
the shape of the slot 8. In this case, the cutting edge of the
blade 9 in an advanced cutting position of the blade 9 extends with
slight clearance relative to the protective cap 6 and the proximal
portion 5 outside of these parts, and the blade 9 may be displaced
into a retracted protected position, in which the blade 9 no longer
projects from the slot 8, and indeed does not project even when the
protective cap 6 has been displaced into the retracted working
position.
[0043] The contour of the blade 9 may differ widely, with it being
possible to use in addition to the helical-line-shaped
configuration according to FIGS. 1 to 3 V-shaped contours or
similar contours, the important point being merely that the cutting
edge projects in longitudinal direction of the obturator 1 from the
introduction tip 3 and that the cutting edge extends over the tip 4
so that, when the obturator is advanced towards a body wall,
starting from the tip a drawing incision is introduced into the
body wall. FIGS. 4 to 7 illustrate possible contours of the blades
9, for example with a shallow or steep ogive (FIGS. 4 and 6) with a
semi-circular contour or with an explicit formation of a tip (FIG.
7).
[0044] The blade 9 is held in the interior of the housing 2 on a
blade carrier 10 that might optionally also be formed integrally
with the blade 9, this blade carrier 10 extending through the
entire housing 2 and closing an opening 11 at the opposite end of
the housing 2 to the introduction tip 3 in the form of a pressure
plate 12. Disposed in the interior of the housing 2 and lying
adjacent to the inner wall thereof is a helical spring 13, which
concentrically surrounds the blade carrier 10 and is supported on
the one hand against the pressure plate 12 and on the other hand
against an annular shoulder 14 of the housing 2 and which displaces
the pressure plate 12 and hence the blade carrier 10 as well as the
blade 10 into a retracted position that corresponds to the
protected position of the blade. By means of a pressure upon the
pressure plate 12 the unit of blade carrier 10 and blade 9 may be
displaced counter to the action of the helical spring 13 in the
direction of the introduction tip 3 so that the blade 9 moves into
the cutting position, in which the cutting edge projects out
through the slot 8.
[0045] The protective cap 6 is connected to a sleeve 15, which
surrounds the blade carrier 10 and is used also to guide the
protective cap 6 and by means of which the protective cap 6 is
mounted in a longitudinally displaceable manner in the obturator 1.
Disposed in an annular gap 16 between the inner wall of the housing
2 and the sleeve 15 is a helical spring 17, which is supported on
the one hand against the inner wall of the housing 2 and on the
other hand against the sleeve 15 and displaces the sleeve 15 and
hence the protective cap 6 into the extended position corresponding
to the inoperative position of the protective cap 6. The protective
cap 6 may be pushed counter to the action of the helical spring 17
into the housing 2 and in this case moves into the working
position.
[0046] A detent lever 18 is moreover mounted in the housing 2 so as
to be pivotable about a pivotal axis extending transversely of the
longitudinal axis and has on one end a detent projection 19 and on
the opposite end a blocking face 20. By means of a helical spring
22, which is supported on the one hand against the inner wall of
the housing 2 and on the other hand against a lateral projection
21, the detent lever 18 is pivoted into an initial position, in
which the detent lever 18 extends parallel to the longitudinal
direction. In this case, the projection 21 lies adjacent to the
annular shoulder 14 (FIG. 9).
[0047] The blade carrier 10 has a lateral detent projection 23,
which projects radially to such an extent that the detent
projection 19 of the detent lever 18 engages into the path of
motion of the detent projection 23 when the blade carrier 10 is
displaced. Both the detent projection 19 and the detent projection
23 have oblique sliding faces 24, 25, which lie adjacent to one
another when the blade carrier 10 is retracted from the advanced
position into the retracted position.
[0048] The blade carrier 10 is surrounded by a sliding ring 26,
which is mounted so as to be longitudinally displaceable along the
blade carrier 10 and the longitudinal displacement of which along
the blade carrier 10 is limited by means of a pin 27, which
projects radially from the blade carrier 10 and engages into an
internal groove 28 of the sliding ring 26 that extends transversely
of the plane of the sliding ring 26. In a manner not evident from
the drawing, the sliding ring 26 lies adjacent to the inner wall of
the housing 2 and is displaceable relative to this inner wall. For
the displacement, however, a specific force is needed in order to
overcome the friction between sliding ring and inner wall.
Consequently, upon a displacement of the blade carrier 10 and hence
of the pin 27 the sliding ring is driven by the movement of the
blade carrier only when the pin 27 strikes against the end of the
internal groove 28.
[0049] The sliding ring 26 on its end facing the introduction tip 3
has a step-shaped recess 29, the outer surface 30 situated
alongside said recess being disposed in the same plane as an outer
surface 32 of an annular flange 31 that is formed on the end of the
sleeve 15 by this annular flange.
[0050] When the obturator 1 is used, the blade carrier 10 is
initially in the retracted position, in which it is displaced by
means of the helical spring 13, the blade 9 therefore being
situated in the retracted protected position. In the retracted
position of the blade carrier 10 the detent projection 19 of the
detent lever 18 is supported on the detent projection 23, with the
result that the detent lever 18 is pivoted out of the initial
position counter to the action of the helical spring 22 (FIG. 8).
The blocking face 20 of the detent lever 18 in this case engages
into a gap between the sliding ring 26 and the annular flange 31.
The protective cap 6 and the sleeve 15 are displaced by the helical
spring 17 into the advanced position, i.e. the protective cap 6 is
situated in its inoperative position. In this position of the
protective cap 6 and the blade 9, the protective cap 6 covers the
blade and the blade does not project from the slot 8. The
protective cap 6 cannot be displaced into the retracted working
position, this being prevented by the engagement of the detent
lever 18 between the sliding ring 26 and the annular flange 31.
[0051] In order to insert the obturator 1, it has to be activated.
This is effected by a pressure upon the pressure plate 12 so that
the pressure plate 12 is displaced counter to the action of the
helical spring 13. In this case, first the detent projection 19
slides down off the detent projection 23, thereby allowing the
detent lever 18 to pivot under the action of the helical spring 22
back into the initial position (FIG. 9).
[0052] As the pressure plate 12 is advanced further, the sliding
ring 26 moves with its outer surface 30 under the blocking face 20
of the detent lever 18 (FIG. 10).
[0053] If the user then releases the pressure plate, the blade
carrier 10 under the action of the helical spring 13 shifts back a
little into the retracted position but at the same time the detent
projection 23 moves into abutment with the detent projection 19,
which prevents any further return movement of the blade carrier 10.
The detent lever 18 moreover rests on the outer surface 30 of the
sliding ring 26, which as a result of the clamping action between
sliding ring 26 and blocking face 20 during this return movement of
the blade carrier 10 is displaced relative to the blade carrier 10,
with it remaining constant in terms of its position relative to the
blocking face 20. As a result of this abutment of the outer surface
30 of the sliding ring 26 with the blocking face 20 of the detent
lever 18, the detent lever 18 is prevented from pivoting out of the
initial position and therefore blocks the full return movement of
the blade carrier 10 into the retracted position (FIG. 12). By
means of the oblique sliding faces 24 and 25 and under the action
of the helical spring 13, which endeavours to displace the blade
carrier 10 into the retracted position, the detent lever 18
experiences a torque that presses its blocking face 20 forcefully
against the outer surface 30 of the sliding ring 26, thereby
ensuring that this blocking is maintained (FIG. 12).
[0054] In this position the blade 9 is advanced into the cutting
position but is still encased by the protective cap 6, which in
turn is situated under the action of the helical spring 17 in the
advanced inoperative position (FIGS. 11 and 12).
[0055] When the obturator 1 is advanced towards a body wall 33, the
tip of the protective cap 6 is positioned against the body wall 33
and therefore pushed back counter to the action of the spring 17 so
that the blade 9, which is in the cutting position, is released
and, when the obturator 1 is advanced further, pierces the body
wall with an incision. The protective cap 6 in this case remains in
position against the body wall 33 and is therefore pushed back
permanently into the working position. A further result of this
backward movement is that the sleeve 15 by means of its annular
flange 31 pushes the sliding ring 26 back relative to the blade
carrier 10, the annular flange 31 at the same time moving under the
blocking face 20 of the detent lever 18 and therefore effecting the
fixing of the detent lever 18 in the axial initial position. The
detent lever 18 therefore remains locked in the detent position,
the locking in this case being effected at the start of the
backward movement of the sleeve 15 by means of the sliding ring 26
and at the end by means of the annular flange 31 (FIG. 14).
[0056] As soon as the obturator 1 has been advanced through the
body wall 33 to such an extent that the protective cap 6 is
disposed inside the body wall 33 (FIG. 15), the protective cap 6
may be displaced under the action of the helical spring 17 forward
into the inoperative position since it is no longer pushed back by
the body wall 33. A further result of this advancing of the
protective cap 6 into the inoperative position is that the annular
flange 31 under the blocking face 20 is pulled away, i.e. the
locking of the detent lever 18 is discontinued and the detent lever
18 may be pivoted out of the paraxial initial position counter to
the action of the spring 22.
[0057] Such a pivoting is effected by virtue of the backward
sliding movement of the blade carrier 10 under the action of the
helical spring 13. During this return movement the sliding faces
24, 25 of the two detent projections 19 and 23 slide along one
another, thereby allowing the detent projection 23 to slide past
the pivoted detent lever 18 and the detent projection 19 thereof
into the retracted position, in which the blade is in the protected
position. The advancing of the protective cap 6 into the
inoperative position therefore triggers a backward sliding movement
of the blade 9 into the protected position, with the result that
the blade 9 no longer projects from the slot 8 and so the risk of
injury ceases to exist as soon as the protective cap 6 has passed
through the body wall 33.
[0058] This instant is reached before the introduction tip 3 has
fully penetrated the body wall 33 because the outside diameter of
the protective cap 6 is smaller than the outside diameter of the
introduction tip 3. Once the introduction tip 3 has been completely
pushed through into the interior of the body, the opening produced
by the blade 9 is expanded without this entailing a further
incision, because the blade 9 in this case is already in the
protected position.
* * * * *